Show menu opening in MacOS 27

That's a symptom of a slow Mac.

Runaway processes and low free storage space are common reasons for Macs to run slow / beachball. 

It is possible there are processes running in the background that are using significant resources. Check Activity Monitor, CPU tab (sort by % CPU) and Memory tab (sort by Memory) to see what's running hard.

Activity Monitor User Guide for Mac - Apple Support

Confirm that you have sufficient free space on your internal storage. The absolute minimum is ~20-25 GB free space, and as a rule of thumb you should aim to have 15-20% of your total internal storage as free space. Terminology is important here – free space is not the same thing as available space. The one that matters is Free space, but what macOS shows in most places is Available space. Available space includes both free space and ‘purgeable’ space, the latter comprises system caches, snapshots and other data that macOS can delete if it decides more free space is needed. However, there is no way the user can force those data to be purged.

The place to check how much Free space you have is in Disk Utility (in Applications > Utilities), by selecting the main container disk below the drive itself (you may need to select View menu > Show all devices to see it). For example, on my M4 MacBook Pro, the Storage settings pane and Get Info on the internal drive show 1.24 TB of Available space, whereas Disk Utility shows there is 1.15 TB of actual Free space, 90 GB less than ‘available’. Although 90 GB is a small fraction of my 2 TB internal storage, that would not be the case with 256 GB or 512 GB of internal storage.

Note that you can also see the Free space in the System Report (System Settings > General > About > System Report button, at the bottom > Storage). 

Some steps to take to safely free up space:

Free up storage space on Mac - Apple Support

Optimize storage space on your Mac - Apple Support

How to free up ‘System Data’ and other st… - Apple Community

If nothing in the above reveals an obvious culprit, then appropriate troubleshooting steps are Safe Mode and creating a new user account to test. 

See if the problem is present when you boot in safe mode. That process performs some system cleanup and clears caches, and also disables 3rd party extensions that may cause problems.

Start up your Mac in safe mode - Apple Support

If that does not correct the issue, test in a new user account. A newly-created user account will have all settings at default, and if the issue does not occur in that new account then it provides guidance on what may need to be changed to correct the issue.

Add a user or group on Mac - Apple Support

Once the testing is complete, the new account can easily be deleted.

Delete a user or group on Mac – Apple Support

If you have 3rd party ‘protection’ software installed, that may be the problem. That includes:

• Cleaners (software claiming to automatically free up space)
• Optimizers (software claiming to make your Mac run faster)
• Antivirus software
• VPN software (unless provided by a school/employer to enable access to internal resources from a remote location)

Such 3rd party system ‘helpers’, ‘cleaners’ and ‘protectors’ do more harm than good. In fact, such products are completely unnecessary for macOS and the only ‘good’ (if you want to call it that) they do is to put money in the developers’ pockets. Cleaners and protectors cause compatibility issues, often after macOS updates. Commercial VPNs claim to hide your browsing activity from websites, and while that may be true those VPN providers just sell your browsing data to others. For the user, all of these types of software offer only harm…and if that is limited to harm to your bank account, then count yourself lucky. If you have installed such software, follow the developer’s instructions to completely uninstall it (note that some developers fail to provide instructions and their software installs can be pervasive, meaning the only way to truly remove it is to erase your Mac, reinstall macOS then restore your user files from a backup).

It might help to download and run EtreCheck, written by a long-time forum member. The free version is fine. Post the full report using the Additional Text button. No personal information is revealed.